WEDNESDAY, June 6 (HealthDay News) -- Keeping off that weight you've lost is possible, a new government study suggests, although no one's claiming it's simple or easy.

"We're still learning about the habits necessary for long-term maintenance of weight," said Dr. Edward Weiss, a medical epidemiologist with the U.S. Centers for Disease Control and Prevention, and lead author of the study published in the July issue of the American Journal of Preventive Medicine.

The good news from the new study? Almost six in 10 people (58.9 percent) who lost weight kept it off for a year. And another 7.6 percent continued to lose weight.

The new study paints a much brighter picture than some other research, which has found that most patients in clinical weight-loss programs regain one-third of their weight in the year after treatment, and that most regain the majority or all of the pounds lost by five years.

But the Weiss-led study does have limitations, he acknowledged. "Some [study participants] may have lost the weight unintentionally," he said. Also, due to the study's methodology, the researchers don't know how the participants lost the weight -- on their own or in an organized program.

Weiss' team examined data from the National Health and Nutrition Examination Survey (NHANES) from 1999 to 2002. It included data from 1,310 U.S. adults, ages 20 to 84, who were overweight or obese and had dropped a substantial amount of weight -- and weighed at least 10 percent less than their maximum weight a year before they were surveyed.

In the United States, an estimated 66 percent of adults are either overweight or obese, according to the CDC.

When the study authors evaluated the respondents' answers to questions about lifestyle habits, Weiss and his team found that those who reported greater daily "screen time" -- television viewing or computer use outside of work -- were more likely to regain weight than those who limited their screen time.

Those who put in four hours or more daily at a computer (not counting work hours at the computer) or watching TV were twice as likely to regain weight as those who put in up to one hour a day. The study authors speculated that time spent at a computer might have displaced exercise time, while those who watched television for several hours may have snacked as they watched.

In another finding, those who didn't meet public health recommendations for physical activity to improve health (moderate activity at least 30 minutes a day, five days a week; or vigorous activity at least 60 minutes a day, three times a week) were twice as likely to regain weight as those who met those recommendations.

It may take less exercise than previously thought to sustain weight loss, Weiss said. He found no differences in regained weight in the group that followed the vigorous exercise guidelines, compared to those who followed the moderate guidelines.

Groups of people may differ in their ability to keep weight off. For instance, Mexican-Americans were twice as likely to regain weight as non-Hispanic whites, but Weiss said this finding needs further research.

Despite the inherent difficulties in studying weight loss and regaining pounds again, and the new study's limitations, Lona Sandon, a spokeswoman for the American Dietetic Association, sees some valuable messages in the new research.

"Exercise is not voluntary once you lose the excess weight," said Sandon, an assistant professor of clinical nutrition at the University of Texas Southwestern Medical Center at Dallas. "It is mandatory for keeping the weight off."

Another key message? "Step away from the television," Sandon said. "TV watching is a behavior associated with weight gain."

"Make lifestyle changes that promote a healthy weight," she added, suggesting changes not only in exercise but in eating habits.

More information

For more on maintaining a healthy weight, visit the U.S. National Heart, Lung, and Blood Institute.

SOURCES: Edward Weiss, M.D., M.P.H., medical epidemiologist, National Center for Chronic Disease Prevention and Health Promotion, Division of Nutrition and Physical Activity, U.S. Centers for Disease Control and Prevention, Atlanta; Lona Sandon, M.Ed., R.D., assistant professor, clinical nutrition, University of Texas Southwestern Medical Center at Dallas, and national spokeswoman, American Dietetic Association; July 2007 American Journal of Preventive Medicine

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